There are two commonly used light weight exterior wall panel systems used in the construction industry today, namely aluminium framed curtain walls and exterior insulated finish system (EIFS).
Aluminium framed curtain wall panels are the most common method for providing exterior walls on multi-story buildings. They have extruded dry-seal systems that protect the building against air and water infiltration and provide superior longevity. A dry seal system can be designed to incorporate the rain screen principle, so the joint can be pressure equalized to help keep moisture away from the seals. The panels can incorporate windows, stone finish or a metal finish. The downside of unitized curtain wall panels is that they perform quite poorly regarding thermal protection of the building.
Exterior insulated panels (sometimes referred to as EIFS) are becoming more commonly used today for multi-story curtain wall construction. When these panels are properly designed and installed, they provide optimum thermal protection for the building. Unfortunately, this type of construction typically requires the joints between the panels to be caulked after the panels are erected. Caulking is what is known as a wet-seal system, they are subject to human error and inclement weather. Caulked joints do not provide the same level of quality and endurance as dry-seal systems and incorporating the rain screen principle is difficult to do with caulked joints. Unfortunately, caulking the joints needs to be done using scaffolding or swing stages located on the outside of the building, this can be costly and makes the work more dangerous to do. The latter is expensive and adds time required to complete the installation. Caulking is also problematic when the proximity of the adjacent building is too close to the new wall to allow access. Additionally, caulking requires skilled labourers and detailed inspection to ensure that the caulked joints are sealed properly.
Dry seal systems for EIFS exist, however they are only capable of sealing relatively small gaps between wall panels with small construction tolerances. This is a problem because aluminium framed curtain wall panels and EIFS typically have large construction tolerances. This means that one cannot use a rigid dry seal because the gap between two panels may vary along the shared length of the panels.
Therefore, it would be advantageous to provide a wet seal system which is easy for unskilled labourers to install.